Electron-discharge device



March 6,1928. 1,661,830

A. w. HULL ELECTRON DISCHARGE DEVICE Filed Nov. 21, 1922 2 Sheets-Sheet 1 Fig. I.

Inventor: Albert W. Hull,

Hls Attorneg.

March 6, 1928.

A. w. HLlLL ELECTRON DISCHARGE DEVICE Filed Nov. 21. 1922 2 Sheets-Sheet Fl 3.

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Patented Mar. 6, 1928.

NIT D STATES PATENT OFFICE.

ALBERT HULL} OF SGHENEGTADY, NEW YORK, ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORPORATION OF NEVT YORK.

ELECTRON-DISCHARGE DEVICE.

Application filed November 21, 1922. Serial No..602,36.

My present invention relates to electron discharge apparatus, and more particularly to the well known type of apparatus in which 7 current is carried across an evacuated space I) between two electrodes one of which is adapted to operate at a substantially higher temperature than'the other and the valueof this current is controlled ,by means of an electrostatic field produced .in the space he- 1 tween the electrodes.

In my U. S. Patent 1,564,852 I have described and claimed a device of the above type in which greatly improved operating ing upon the space between the electrodes an auxiliary magnetic field produced by a magnetizing coil external to the device.

In my U. S. Patent 1,5235778, I have described and claimed an electron discharge device in which the current flowing between the electrodes is controlled b means of a magnetic field produced by the current employed for heating the heated electrode.

Ihave now discovered that the control principle set forth in my Patent 1,523,778 may be utilized to advantage in obtaining the results set forth in my Patent 1,564,852.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims;

may be used in a device for carrying out certain aspects of my invention and Figs.

6 and 7 show characteristic curves of devices with which my invention is employed.

I have indicated in Fig.1 an electron discharge device comprising a linear filamentary receptacle 4.

characteristicsmay be obtained by impresscathode 1 of large diameter adapted .to be heated, a grid electrode 2 constructed of longitudinal slats and a cylindrical anode 3 surrounding the grid and cathode. The grid and anode are preferably arranged in circular synnnetry about the cathode and the electrodes are all enclosed in the evacuated lVith a filamentary cathode of large diamctersuch asis necessary to employ to carry myinvention into effect, special circuitconnections are provided to obviateucracking of the sealat, theterminals as the cathode expands and contracts. In the present case I have indicated leading-in conductors 5 and 6 for supplying current to the cathode, these conductors being sealed into the receptacle 4 at the points 7 and 8. Theleadingin conductor 5 is joined to the cathode 1 by means of a spring 9 consisting preferably of tungsten and fiexibleconductors'lfi which surround, this spring connecting the leading-in conductor to the cathode and carry the greater part of the heating; current. The grid electrode is supported by two bands 11. and 12 which surround suitably formed tubular portions of the receptacle. The band. 12

is clamped to the tubular portion of there- 7 ceptaclo which it-surrounds and the leadingin conductor 13. which is sealed into the receptacle at the point 14-, is connected thereto. The band 11 maybe free to slide back and forth along the tubular portion of .the receptacle which it surrounds to provide for expansion and contraction of the grid. Similarlytheanode is supported by means of the supporting arm 15 which is attached to the two bands 16 and 17, leading-in con- 8 ductor 18 being connected to the band; 17.

In the circuit arrangement shown in Fig. 2 the cathodel is heated by means of the source of current which is indicated dia grammatically by a battery 19. circuit between the cathode 1 and the grid. 2 includes a coil 20, which is coupled to coil 21, which is included in the output circuit between cathode 1 and anode 3, this output cir- An input of the device.

cuit including the usual source of current 22. Coil 21 is coupled to the coil 23 in the circuit of the antenna 24- by means of which high frequency oscillations may be supplied to the antenna.

If the diameter of the cathode is relatively small the magnetic field produced by the heating current will be so small that it.

ordinarily required to render incandescenta filamentof this size. When the supply voltage is as low as about one volt, the heating current in a filament of 7 mils diameter is sufiicient to produce an appreciable decrease of electron current by what I term magneto-strictive effect. This effect is produced by reason of the tendency of the magnetic field to deflect the electrons and cause them to move in curvedorb ts located 1n planes parallel to and ln'cludmg the axis of the cathode instead of in straight lines. In general, the voltage necessary to overcome this inagneto-strictive efi'ect of a current required to render incandescent a tungsten filament is substantially proportional to the cube of the diameter of the cathode.

In carrying out my invention I construct my device with a filament/of such size or current-carrying capacity in proportion to the desired operating voltage that under certain predetermined operating ranges of grid potential this magneto-strictive effect will influence the flow of current in a desired manner.

In Fig. 5 I have shown curves representingthe relation between grid potential and anodecurrent of a three electrode device under diflerent conditions of operation. Curve A is a typical characteristic of a three-electrode device of the ordinary construction as ordinarily operated. Curve B shows a corresponding characteristic when the magnetic field produced by the heating current flowing in the cathode is of sufiicient value to appreciably influence the flow of current. It will be observed that in curve B the anodeeurrent instead of decreasing gradually as the grid becomes more negative decreases very rapidly as the grid becomes negative and reaches a substantially zero value at a less negative grid potential than in the case where no appreciable magnetic field is present. The portion of the curve B between the points 6, and e, is much steeper than any portion of curve A, therefore a much. greater degree of amplification would be obtained by the device over this range than when the device is operated without the magnetic field. It should also be noted that at the points c and 6 there are much more abrupt changes than are found on curve A. Either of these points therefore may be advantageously employed for operating the device as a detector.

The value of the grid ]')otcntial at which the flow of current will be interrupted depends in any particular device upon the strength of the magnetic field. I11 general, the stronger the magnetic field the more positive or less negative the grid potential at which cutofi' occurs- In general also, the stronger the magnetic field the steeper the slope of the current curve.

In Fig. 6 I have indicated a characteristic curve in the case where the magnetic field is strong enough to cutoif the current when there is a 'fairly high positive potential on the grid. This adjustment may be employed adwmtageously in devices utilized for producing oscillations. The curve C in Fig. 6 shows the time relation and amplitude of the grid potential when oscillations are produced. It will be seen from this curve taken in conjunction with curve B that current is supplied to the anode only during intervals represented by the shaded portions of curve C. It will be noted that with the arrangement shown and described it is not necessary to employ any grid leak or biasing battery to adjust the normal grid potential but that efficient operation may be maintained by so proportioning the dimensions of the cathode and the spacing of the electrodes therefrom that the magnetic field produced will shorten the time in each cycle of the grid potential during which current will flow. In case the grid oscillations are properly phased with respect to the oscillations of the anode potential, this arrangement will result in a greater efficiency of operation of the systen'i than when current is supplied to the anode during the greater part of the cycle of the grid potential.

' By the use of a grid construction such as is indicated in Fig. 3, additional ad vantages in operation may be obtained. The grid in this case is constructed of rings 25. These rings are arranged inplanes perpend cular to the axis of the cathode and are supported by arms 26 which pass through holes in the rings. Spacing members .27 surrounding the arms 26 maintain the desired spacing oi? the rings25. The effect of the magnetic field produced by the heating current of the filament in this case will be to deflect the electrons causing them to strike the grid rings 25 instead of passing between them as would be their tendency if they were moving in straight lines. If the potentials applied to the electrodes are properly chosen each electron which is caused to strike the grid in loo lHI

this manner may produce several secondary or impact electrons which will travel to the more positive anode. As a result the current produced in the output circuit may be several times the current which will be produced therein by the primary electrons emitted by the cathode. lVhen the device is employed as an amplifier this phenomenon may be utilized to increase the amplification obtained, and when it is used as an oscillator the amplitude of the oscillations produced may be greatly increased by reason of this phenomenon. In most'cases the emission of the secondary electrons from the grid will preferably be of great enough magnitude to produce a negative resistance characteristic in the grid circuit. This characteristic may be utilized to increase the amplification which may be obtained, and also for producing oscillations. v

In Fig. 4 I have shown a circuit arrangement which is specially adapted for utilizing this negative resistance characteristic for the production of oscillations. In this case an oscillating circuit comprising inductance 28 and variable capacity 29 is connected between cathode l and grid 2; Oscillations will be produced in this grid circuit, the frequency of the oscillationsbeingdeterruined by the resonant frequency of the oscillating circuit, and the potential of the grid 2 will be caused to vary in accordance with the. oscillations produced with the result that greatly amplified oscillations may be supplied from the coil 30 in the output circuit to the antenna 24. In this case it will be necessary to first impress a positive charge upon the grid before oscillations will start. This may be accomplished by connecting one terminal of the condenser 29 by a switch 32 and the connection 31 to a pointin the bate tery 22 instead of directlyto the cathode.

luthe curves shown in Figs. 5 and 6, it

assumed that thereis not sutlicient secondary impact emission produced from the grid to produce any appreciable efiiect in thc current in the output circuit. The effect of large impact emission from the grid is indiproduced by the magnetic field, and curve D shows the relation between grid current and grid. potential, these curves being negative or in, the opposite direction tothe usual grid on rent by reason of the secondary emission. Curve B'indicates the resultant current in the output circuit produced by the primary electrons which reach the anode and the sec. ondary or impact electrons from the grid which flow to the anode. By reason of the high secondary emission the current which may be supplied to'the output circuit is much greaterthan that which would be supplied by Letters Patent of the United States, is 1-.

1. An electron discharge device comprising a cathode, an anode and a controlling grid, said electrodes being so spaced and the cathode beingof such current carrying capacity that with an anode voltage not exceed-- ing' a predetermined value the normal current required to heat the cathode to a given operating temperature will produce in the space surrounding the cathode a magnetic field .of such value as to increase substantially over a predeterminedoperating range the change in anode current per unit change in grid voltage over its change in the absence of such magnetic field.

2. An electron discharge device comprising a cathode, an anode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another and so proportioned that with an anode voltage not exceeding a predetermined value the normal current required to heat the cathode to a given operating temperature will produce in the space surrounding the cathode a magnetic field of such value as to increase substantially over a predetermined operating range, the change in anode current per unit change in grid voltage over its change in the absence of such magnetic field. I g

, 3. An electron discharge device comprising a cathode, ananode and a controlling grid, said electrodes being arranged in sub stantially circular symmetry with respect to one another, said-cathode being of such current-carrying capacity that the normal current required to heat it to a given operating temperature will produce in the space between the electrodes with an anode voltage not exceeding a predetermined value a magnetic field of such value as to greatly increase over a predetermined operating range the change in anode current per unit change in 2 grid voltage over its change in the absence of such magnetic field.

4t. An electron discharge device pacity that the normal current required to comprise ing a cathode, an anode and acontrollnnr heat the cathode to a given operating tom pera-ture will produce in the space surrounding the cathode a magnetic field of such value as to prevent any electrons from reaching the anode over a predetermined operating range of grid potential and with an anode voltage not exceeding a predetermined value.

5. An electron discharge device comprising a cathode, an anode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another and the cathode being of such current carrying capacity that the normal current required to heat the cathode to a given operating temperature will produce in the space surrounding the cathode a magnetic field of such value as to prevent any electrons from reaching the anode over a predetermined operating range of grid potential and with an anode voltage not exceeding a. predetermined value.

6. The combination with an electron discharge device having a cathode, an anode and a controlling grid, said electrodes being arranged in substantiallyv circular symmetry with respect to one another of a circuit between cathode and anode, means for impressing an alternating potential on said grid and means for supplying heating current to the cathode, the electrodes being so arranged and proportioned that with an anode voltage not exceeding a predetermined value the magnetic field produced by the heating current fiowing in the cathode will greatly shorten the time in each cycle of grid potential during which current will fiow to the anode over the time during which current would flow in the absence of such magnetic field.

7 The combination with an electron dis charge device having a cathode, an anode, and acontrolling grid of a circuit between cathode and anode, means for impressing an alternating potential on said grid, and means for supplying heating current to the cathode, said cathode being of such current-carrying capacity that with an anode voltage not exceeding a predetermined value the magnetic field produced by the heating current flowing in the cathode will greatly shorten the time in each cycle of grid potential during which current will flow to the anode over the time during which current would flow in the absence of such magnetic field.

8. The combination with an electron discharge device having a cathode, an anode, and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another, of a circuit between cathode and anode, means for impressing an alternating potential on said grid,and means for supplying heating current to the cathode, said cathode being of suchcurrentcarrying capacity that with an anode voltage not exceeding a predetermined value the magnetic field produced by the heating current flowing in the cathode will greatly shorten the time in each cycle of grid potential during which current will flow to the anode over the time during which current would flow in the absence of such magnetic field.

9. An electron discharge device comprising a cathode adapted to be heated, an anode and a. controlling grid electrode, said elecirodes being so spaced and proportioned that the normal current required to heat the cathode to a given operating temperature will produce in the space surroundingthe cathode with an anode voltage not exceeding a predetern'iined value a magnetic field of such value as to appreciably modify the controlling effect of an electrostatic field on the grid electrode.

10. An electron discharge device comprising an electron emitting- 'athodc, an anode and a controlling grid, said cathode being of such current carrying capacity that it is capable of functioning both as a source of electrons and as a means for producin a magnetic field of sutficicnt strength to etleclively decrease the electron current between cathode and, anode with a given impressed on the grid and with an anode voltage not exceeding a predetermined value;

12. An electron discharge device comprising an electron emitting cathode, an anode and a controlling grid, said cathode being of such current carrying capacity that with an anode voltage not exceeding a predetermined value the magnetic field produced by the currentflowing therein will be of sullicienit strength to deflect electrons emitted by said cathodein curved orbits thereby e'llectively decreasing the electron current between cathode and anode with a given impressed voltage on the grid.

18. An electron discharge device comprising a cathode adapted to be heated, an anode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another and the cathode being of such current carrying capacity that the normal current required to heat the oath ode to a given operating temperature will produce in the space surrounding the cathso spaced. and the cathode being ofsuch cur- 7 rent carrying capacity that the normal current required to heat the cathode to a given operating temperature will produce in the space surrounding the cathode a magnetic field of such value that over a predetermined operating range of grid potential and with an anode voltage not exceeding a predeter mined value the current flowing in an output circuit connected to the anode will, due to'the emission of impact electrons from the grid be greatly increased over its value in the absence ofthe magnetic field.

15. The combination. With an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid, of meansforvarying the potential of said grid and an output circuit connected to the anode, said electrodes being so arranged and proportioned that the normal current required to heat the cathode to a given operating temperature will produce in the space surrounding the cathode a magnetic field of such .value thatover a predetermined operating range of grid potential and with an anode voltage. not exceeding a predetermined value the current supplied by said output circuit Will, due to the emission of impact electrons from the grid be greatly increased over its value in the absence ofthe magnetic field.

16.. The combination with an electron discharge device having a cathode adapted to be heated, an anode and acontrolling grid, said electrodes being arranged. in substantially circular symmetry with respect to one another, of means for varying the potential of said grid, and an output circuit connected to said anode, said electrodes being so arranged and proportioned that the normal current required to heat the cathode to a given operating temperature will roduce in the space surrounding the catho e a magnetic field of such value'that over a predetermined operating range of grid potential and with an anode voltage not exceeding a predetermined value the current supplied by said output circuit will, due to the emission of impact electrons. from thegrid be greatly increased over its value in the absence of the magnetic field.

17. The combination with an electron discharge device having a cathode adapted to be heated, an anode and a controllinggrid,

of means for varying the potential of said grid, an output circuit connected to; said anode and means for producing in the space surrounding the cathode by the current required to heat the cathode to a given opcrating temperature, a. magnetic field of such value that over a predetermined operating range of grid potential and with ananode voltage not exceeding a predetermined value the current supplied by said output circuit will, due to the emission of impact electrons from the grid be greatly increased Evil-",3 its value in the absence of the magnetic '18. The combination with an electron discharge device having acathode adapted to be heated, an anode and a controlling grid,

said electrodes being'arranged in substan- 'tially circular symmetry with respect to one another, or means for varying the potential or said grid,'an output circuit connected to said anode and means for producing in the space surrounding the cathode by the current required to heat the cathode to a given operating temperature, a magnetic field of such value'that over a predetermined operating range of grid potential and with an.

anode, voltage not exceeding a predetermined value the current supplied by sald output circuit will, due to the emission of impact electrons from. the grid be greatly increased over its value in the absence of the magnetic field.

19. The combination with an electron discharge device having a cathode adapted to .grid, an output circuit connected to said anode, means for producing by the current required to heat said cathode to a given opcrating temperature a magnetic field in the space between said electrodes, and means independent of said magnetic field for producing'oscillations in said output circuit, said device being so constructed and the magnetic field being of such strength that over a predetermined operating range of grid potential and with an anode voltage not exceed-' ing a predetermined value the amplitude of the oscillations supplied by said output cir- I cuit will, due to the emission of impact electrons'from the grid, be greatly increased over their amplitude in the absence of the magnetic field. r

20. The combination with an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid,

said electrodes'being arranged in substantially circular symmetry with respect to one another, of means for varying the potential of said grid, an output circuit connected to said anode, means for producing by the current required to heat said cathode to a given operating temperature a magneticfield in the space between said electrodes, and means independent of said magnetic field for pro duclng oscillations 1n said output circuit,

said device being so constructed and the due tothe emission of impact electrons from the grid, be greatly increased over their amplitude in the absence of the magnetic field.

21. The combination with an electron dis charge device having a cathode adapted to be heated, an anode and a controlling grid,

of means for varying the potential of said grid, an output circuit connected to said anode, means for passing current through said cathode to heat it to a given operating temperature, and means independent of the magnetic field produced by the heating current for producing oscillations in said output circuit, said device being so constructed and the magnetic field produced by the current flowin in said cathode for heating-it to a desired operating temperature being of such strength that over a predetermined operating range of grid potential and with an anode voltage not exceeding a predetermined value the amplitude of the oscillations supplied by said output circuit will, due to the emission of impact electrons from the grid, be greatly increased over their amplitude in the absence oi. the magnetic field.

22. The combination with an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid, said electrodes being arranged in substan tially circular symmetry with respect to one another, of means for varying the potential of said grid, an output circuit connected to said anode, means for passing current through said cathode for heating it to a given operating temperature and means independent of the magnetic field produced by the heating current for producing oscil-c lations in said output circuit, said device being so constructed and the magnetic field produced by the current flowing in said cathode for heating it to the, given operating temperature being of such strength that over a predetermined operating range of grid potential. and with an anode voltage not exceeding a predetermined value the amplitude of the oscillations suplied by said. output circuit will, due to the emission of impact electrons from thegrid, be greatly increased over their amplitude in the absence of the magnetic field.

23. The combination with an electron dis charge device having-a cathode adapted to beheated, an anode and a controllmg grid of an oscillating circuit connected between said cathode and said grid and an output circuit connected to said anode, said electrodes being so arranged and proportioned and the potentials applied to said electrodes being so chosen that the normal current required to heat the cathode to a given operating temperature will produce in the space surrounding said cathode a magnetic field of such value that an emission of impact electrons from said grid will be produced of suiiicient amount to produce a negative resistance in the circuit between cathodev and grid and cause the generation of oscillations in the oscillatory circuit. v

24. The combination with an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid of a control circuit connected between said cathode and said gridand an output circuit connected to said anode, said electrodes being so arranged and proportioned and the potentials applied to said electrodes being so chosen that the normal current required to heat the cathode to a. given operating temperature will produce in the space surrounding said cathode a magnetic field of such value that an emission of impact electrons from said grid will be produced of suflicient amount to produce a negative resistance in the circuit between cathode and grid. i

25. The combination with an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another, of an oscillating circuit connected between said cathode and said grid, said electrodes being so arranged and proportioned and the potentials applied thereto being so chosen that the normal current required to heat the cathode to a given operating temperature will produce in the space surrounding said cathode a magnetic field of such value that an emission of impact electrons from said grid will be produced of sutficient amount to produce a negative resistance in the circuit between cathode and grid and cause the generation oi. oscil lations in the oscillatory circuit.

26. The combination with an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another of a control circuit connected between said cathode and said grid and an output. circuit connected to said anode, said electrodes being so arranged and proportioned and the potentials applied thereto being so chosen that the normal current required to heat the cathode to a given operating temperature will produce in the space surrounding said cathode a magnetic field of suclrvalue that an emission of imoperating temperature will with an anode voltagenot exceeding a predetermined value produce in the space surrounding the oathode a magnetic field of such value as to defleet electrons emitted by said cathode in curved orbits and cause an increase in the number of electrons striking the third electrode.

28. An electron discharge device comprising, a linear cathode adapted to be heated,

an anode and a third electrode interposed between cathode and anode, said third electrode comprising fiat conducting members arranged in planes intersecting the axis oi? said cathode, said electrodes being so arranged and the cathode being of such current carrying capacity that with an anode voltage not exceeding a predetermined value the normal current required to heat the cathode to a given operating temperature will. produce in the space surrounding the cathode a magnetic field of such value as todefiect electrons emitted by said cathode in curved orbits and cause the major portion of the electrons emitted to strike the third 1 electrode.

29. The method of operating an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid which consists in producing a flow of electrons between cathodeand anode, impressing a variable potential upon the grid and producing by means of the current required to heat the cathode to a given operating temperature a magnetic field in the space between the electrodes of sufiicient magnitude to greatly increase over a predetermined operating range the change in anode current per unit change in grid'potential over its change in the absence of such magnetic field.

30. The method of operating an electron discharge device having a cathode adapted to be heated, an anode and acontrolling grid and an output circuit connected to the anode which consists in producing a flow of electrons between cathode and anode, impress ing a variable potential-upon the grid and producing by means of the current required to heat the cathode to a given operating temperature a magnetic field in the space between the electrodes of sufficient magnitude to cause an emission of impact electrons from the gridand thereby increase over a predetermined operating. range of grid potential the current flowing in the output circuit over the value of such current in the absence of a magnetic field.

The method of operating an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid and an output circuit connected to the anode which consists in producing a flow of electrons between cathode and anode, producing oscillations in the output circuit by applying a control potential to the grid and producing by means of the current required'to heat the cathode to a given operating temperature a magnetic field in. the space between the electrodes of such Value that the amplitude of the oscillations produced in the output circuit will be greatly increased over their amplitude in the absence of the magnetic field.

32. The method of operating an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid andan output circuit connected to the anode which consists in producing a flow of electrons between cathode and anode, producing by means of the current required to heat the cathode to a given operating temperature a magnetic field in the space between the electrodes of suflicient value to cause a suflicient emission of impact electrons from the grid to produce a negative resistance in a circuit between cathode and grid, utilizing this negative resistance to produce oscillations and thereby vary the potential of the grid and supplying corresponding oscillations of greater amplitude from the output circuit.

L3. The method of operating an electron discharge device having a cathode adapted to be heated, an anode and a controlling grid which consists in producing a flow of electrons between cathode and anode, impress ing an alternating potential upon the grid and producing by means of the current required to heat the cathode to a given operating temperature a. magnetic field in the discharge device having a cathode adapted to be heated, an anode and a controlling grid and an output clrcuit connected between cathode and anode which consists in producing a flow of electrons between cathode and anode, impressing an alternating po- .tential upon the grid and producing by means of the current required to heat the cathode to a given operating temperature a magnetic field in the space between the electrodes of suflicient magnitude to cause an increase in the emission of impact electrons 5 from the grid and thereby increase over a predetermined range of grid potential the current flowing in the output circuit and greatly increase over a predetermined operating range the change in grid potential over its Cphange'in the absence of such magnetic fiel In Witness whereof, I have hereunto set my hand this 20th day of November, 1922. ALBERT WV. HULL. 

